Field of the Invention
This invention relates to a developing cartridge capable of being attached and detached with respect to the body of an image forming apparatus and an image forming apparatus that forms an image on a recording medium using electrophotographic technology.
Description of the Related Art
In an image forming apparatus such as a printer using an electrophotographic process, a photosensitive drum is first uniformly charged. The charged photosensitive drum is selectively exposed to form an electrostatic latent image on the photosensitive drum. The electrostatic latent image formed on the photosensitive drum is developed by a toner to form a toner image on the photosensitive drum. The toner image formed on the photosensitive drum is transferred onto a recording medium such as paper. The toner image transferred onto the recording medium is heated and pressurized to fix the toner image on the recording medium.
For such an image forming apparatus, maintenance of respective process means (such as a photosensitive drum, developing device, and a charge roller), a toner refill, and the like are necessary. Thus, in order to facilitate maintenance of respective process means, a toner refill, and the like, a process cartridge has been put into use in which a photosensitive drum, a charge roller, and a developing device are integrated. Such a process cartridge is attachable and detachable with respect to the body of an image forming apparatus. By replacement of a process cartridge, a user can perform maintenance of the respective process means, a toner refill, and the like.
In some process cartridges, a photoreceptor cartridge in which a cleaning blade to clean the surface of a photosensitive drum, the photosensitive drum, a charge roller, and the like are integrated and a developing cartridge in which a developing roller and the like are integrated are capable of being attached and detached separately. In such cases, the photoreceptor cartridge and the developing cartridge can be replaced individually. In the case where such a design is employed, a photoreceptor cartridge and a developing cartridge can each be replaced respectively at an appropriate timing.
Such a design in which a photoreceptor cartridge and a developing cartridge are replaced individually often employs a mechanism to cause a photosensitive drum and a developing roller to come into contact or separate. During replacement of the developing cartridge, the developing cartridge is inserted to the body of an image forming apparatus in a state where the developing roller is separated from the photosensitive drum, so that the developing roller does not slide against the photosensitive drum.
In recent years, image forming apparatuses that form a color image using a plurality of colors of toners have become widespread. In such color image forming apparatuses, photosensitive drums respectively corresponding to the plurality of colors of toners are arranged in a single line along the moving direction of an intermediate transfer belt that is for a primary transfer of a toner image formed on the photosensitive drum. Such image forming apparatuses are called inline image forming apparatuses. In some inline image forming apparatuses, a plurality of photosensitive drums are arranged in a single line in a direction intersecting with the vertical direction. An inline design can easily meet the demands for increasing the speed of image formation or application in a multifunction printer.
In a technique disclosed in Japanese Patent Application Laid-open No. 2014-102425, a cover provided to the body of an image forming apparatus is opened, at the time of attachment of a developing cartridge to the image forming apparatus, to expose an opening provided to the body. From that opening, the developing cartridge is inserted into the body. In a state where the developing cartridge is being inserted to the body, the developing cartridge is guided by a guide rail to bring about a state where a developing roller is separated from a photosensitive drum. Closing the cover in a state where the developing cartridge has been attached to the body causes the guide rail guiding the developing cartridge to move, such that the developing roller comes into contact with the photosensitive drum.
In the technique disclosed in Japanese Patent Application Laid-open No. 2014-102425, the developing cartridge is attached to or detected from the body while being guided by the guide rail that is movable with respect to the body. Due to a slight gap between the developing cartridge and the guide rail, a slight movement of the developing cartridge with respect to the guide rail may occur at the time of attachment or detachment of the developing cartridge. Accordingly, there have been cases where the developing cartridge wobbles with respect to the body. In such cases, there is a risk of the developing roller making contact with the photosensitive drum. It is conceivable to provide a sufficient gap between the developing roller and the photosensitive drum to prevent the developing roller and the photosensitive drum from making contact. However, in the case of providing the sufficient gap between the developing roller and the photosensitive drum, there has been a risk that the image forming apparatus increases in size. In the case of providing the gap between the developing roller and the photosensitive drum in the inline design described above, there has been a risk that the image forming apparatus further increases in size in the direction in which the photosensitive drums are aligned.